Clay Shirkey nominates the Pareto Principle. We have the idea in our heads that most distributions fall along a bell curve (most people are in the middle). But this is not how the world is organized in sphere after sphere. The top 1 percent of the population control 35 percent of the wealth. The top two percent of Twitter users send 60 percent of the messages. The top 20 percent of workers in any company will produce a disproportionate share of the value. Shirkey points out that these distributions are regarded as anomalies. They are not.

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Helen Fisher, the great researcher into love and romance, has a provocative entry on “temperament dimensions.” She writes that we have four broad temperament constellations. One, built around the dopamine system, regulates enthusiasm for risk. A second, structured around the serotonin system, regulates sociability. A third, organized around the prenatal testosterone system, regulates attention to detail and aggressiveness. A fourth, organized around the estrogen and oxytocin systems, regulates empathy and verbal fluency.

This is an interesting schema to explain temperament. It would be interesting to see others in the field evaluate whether this is the best way to organize our thinking about our permanent natures.